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BULLETIN  NO     1. 


Division  of  Entomology.    ♦ 


I  Board  of   Commissioners  of  Agriculture  t 


and  Forestry. 


TERRITORV     OF     HAWAII. 


I  Tfie  Leaf-Hopper  of  the  5uoar  Cane  I 


R.  C.  L.  PERKINS, 

ASSl^TAXT  EXTOMOLOGIST. 


U023 


/r^-  / 


IIONOLFLr,  li.  T. 

PIAWAIIAN   GAZETTE    CO.,    Ltd 

1903. 


♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦  ♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦^.♦♦♦♦♦^ 


BULLETIN  NO.  1.  Division  of  Entomology. 

Board  of   Commissioners  of  Agriculture 
and  Forestry. 

TEIRRITORY     O  F^     HANA/AII. 


The  Leaf-Hopper  of  the  Sugar  Cane 


R.  C.  L.  PERKINS, 

ASSISTANT  ENTOMOLOGIST. 


HONOLUEU,  H.  T. 

HAWAIIAN   GAZETTE    CO.,    Ltd. 

1903. 


Board  of  Commissioners  of  Agriculture  and 
Forestry. 


IONOL_UI_U,     T. 


ORRICETRJ 


M  e:  M  B  e:  R  s . 

J.  F.  Brown 

A.  W.  Carter  L.  A.    Thurston, 


Prf'sideid. 


J.  D.  Dole 

W.   M,    GiFFAKD 

L.  A.  Thurston  H.  E.  Cooper, 

H.  E.  Cooper 


Secretary  ami  Exei  ullve  Officer. 


DIVISION      OR      ElM-rOMOLOCBY. 

A,   KoEBELE.  SuperihUmUnt  of  Entvviohgy. 
R.  C.  L.  Perkins,  Aadstanl  Entomuhgisl. 


Honolnki,  Aug-nst  ist,   1903. 

Tlic  Coiiiiiiissioiicrs  of  Agriculture  of  the  Territory  of  Ha7vaii: 

Gentlemen : 

In  the  absence  of  the  Superintendent  of  Entomology,  I  here- 
with submit  for  publication  a  report  on  the  subject  of  the  leaf- 
hopper  of  the  sugar-cane,  an  insect  imported  into  these  islands 
during  recent  years.  I  have  already  reported  very  fully  at  in- 
tervals during-  the  last  twelve  months  on  most  points  connected 
vvitli  this  leaf-hopper  attack  to  various  members  of  the  Hawaiian 
Sugar  Planters'  Association,  and  some  of  these  reports  have  been 
printed  in  their  publications.  For  the  sake  of  completeness,  I 
have  here  repeated  matter  contained  in  some  of  these  reports, 
though  at  less  length.  Appended  also  are  some  important  notes 
on  the  subject  of  chemical  treatment  of  seed  cane  containing  eggs 
of  the  leaf-hopper,  with  a  view  to  destroying  these  without  in- 
jury to  cane.  These  notes  were  kindly  furnished  me  by  Mr.  C.  F. 
Eckart,  Director  of  the  Experiment  Station,  at  Makiki,  and  the 
experiments  on  which  they  are  based  were  conducted  with  the 
greatest  care  and  exactness.  More  than  a  year  ago  I  declared 
the  necessity  of  making  these  experiments  and  it  is  fortunate  that 
Mr.  Eckart  has  been  able  to  make  them. 

R.  C.  L.  PERKINS. 


History  of  tie  Occurrence  of  the  Siigar-Cane 
Leaf-Hopper*  in  Hawaii. 

I.  In  the  latter  half  of  the  year  1900  I  first  ohsen'ed  and  col- 
lected specimens  of  the  leaf-hopper  of  the  cane,  but  it  was  not 
until  the  end  of  190 1  or  the  early  part  of  1902,  that  it  came  under 
my  notice  as  doing  quite  serious  damage  locally  on  Oahu,  and  still 
some  months  later  when  its  ravages  were  reported  as  being  more 
extensive  and  it  was  submitted  from  one  of  the  other  islands — 
namely,  Kauai. 

Tn  my  report  written  on  Nov.  15th,  1902,  I  remarked:  "This 
small  insect  is  highly  injurious  to  cane  and  its  destructiveness 
threatens  to  exceed  that  of  the  cane-borer" — a  statement,  as  the 
secjuel  proves,  by  no  means  exaggerated. 

As  for  various  reasons  it  was  not  possible  for  me  at  that  time 
personally  to  visit  the  windward  islands,  during  Mr.  Koebele's 
absence  from  the  Territory,  I  strongly  advised  that  precautions 
should  be  taken  to  keep  the  pest  from  being  carried  thither  in 
seed  or  other  cane,  on  the  supposition,  or  rather  in  the  hope,  that 
it  had  not  already  become  established  there. 

Not  long  afterwards,  however,  I  learnt  that  it  was  already 
strongly  established  both  on  Maui  and  the  Northern  parts  of  Ha- 
waii, and  that  any  precautions  against  its  introduction  were  there- 
fore unnecessary. 

From  that  time  to  the  present,  samples  of  cane  attacked  by  the 
leaf-liopper  have  been  brought  to  me  for  examination  constantly 
from  all  the  sugar-growing  islands  and  most  districts  of  these 
islands,  as  well  as  many  insects  or  other  creatures  supposed 
(risjhtlv  or  wronelv)  to  be  attacking  these. 


For  description  see  Appendix  (note  IV.) 


G 

Judging  from  observations  made  by  me  on  otber  imported  in- 
sects, to  the  rate  of  increase  of  which  I  have  paid  special  at- 
tention, I  should  consider  that  the  leaf-hopper  was  introduced 
two  or  three  years  prior  to  1900;  but  that  until  1900  it  was  not  in 
such  numbers  that  it  would  be  likely  to  come  under  the  observa- 
tion even  of  an  entomologist,  except  by  the  merest  chance.  It  is 
t'"ue  that  some  plantation  managet  s  think  the  leaf-hopper  has  been 
present  on  their  plantations  for  many  years,  but  this  is  certainly  an 
error  of  identification.  During  six  years'  continuous  collecting, 
from  1892  to  1897,  when  I  formed  a  large  collection  of  leaf-hop- 
pers of  many  species  and  from  every  island,  I  never  met  with 
a  single  individual  of  the  present  pest. 

It  is  incredible  that  a  species  which  is  always  gregarious,  which 
produces  on  the  cane  the  most  obvious  and  characteristic  outward 
signs  of  its  presence,  and  which,  when  mature  is  readily  attracted 
to  the  lights,  should  have  entirely  escaped  my  notice.  Then,  again, 
it  was  one  of  the  first  species  noticed  and  collected  by  me  on  my 
return  to  active  field  work  in  1900.  In  the  early  days  of  my  col- 
lecting here  an  allied  species  of  leaf-hopper  was  known  to  me  to 
frequent  the  cane-fields  iu  small  numbers,  and  this  would  cer- 
tainly not  have  been  distinguished  from  the  present  pest  except 
by  a  more  careful  comparison  than  a  non-entomologist  would  be 
likely  to  make.  To  sum  up,  it  can  be  stated  most  positively  that 
the  present  leaf-hopper  attack  is  due  to  a  pest  comparatively  re- 
cently introduced  into  the  islands  and  not  by  one  of  old  standing, 
which  has  suddenh'  become  injurious,  as  some  are  inclined  to 
think. 

THE  HAWAIIAN  LEAF-HOPPER,  AN  AUSTRALIAN  SPECIES  AND  NOT 
IDENTICAL  WITH  ANY  OF  THE  HITHERTO  KKPORTED  SUGAR 
PESTS    IN    OTHER    COUNTRIES. 

2.  Seeing  then  that  our  leaf-hopper  was  an  imported  species, 
in  a  Report  to  the  Hawaiian  Sugar  Planters'  Association,  written 
on  Nov.  15th,  1902,  I  stated  that  it  was  of  the  utmost  importance 
for  us  to  learn  whether  our  leaf-hopper  \\ere  one  of  those  al- 


ready  known  to  attack  cane  in  other  countries  or  some  species 
hitherto  unknown  as  a  pest,  and  in  the  latter  event  whence  it 
liad  been  imported.  Obviously,  if  the  species  proved  to  be  West 
Indian  we  did  not  want  to  send  to  Java  tO'  look  for  natural 
enemies. 

Such  literature  as  was  to  be  procured  in  the  islands  dealing 
with  leaf-hoppers  injurious  to  cane  I  examined  with  great  care, 
and  in  a  report  written  to  Mr.  Tenney  of  the  Planters'  Associa- 
tion on  October  23rd,  1902,  I  expressed  my  opinion  that  the  Ha- 
waiian pest  "was  certainly  none  of  these,"  and  reiterated  this  in 
my  report  of  Nov.  15th  above  mentioned.  At  the  same  time  I 
called  attention  to  the  similarity  in  habits  between  the  pest  here 
and  the  Javanese  species(Dicranotropis  vastatri.v).  Finally,  after 
much  correspondence  with  other  countries,  the  matter  was  con- 
clusively settled  for  me  by  Mr.  Kirkaldy,  who  obtained  from  Ger- 
many cotypes  of  the  Javanese  insect  described  by  Breddin  and 
found  it  to  be  quite  distinct  from  the  Hawaiian  one.  Other  au- 
thorities considered  the  Javanese  insect  and  ours  identical. 

■Meanwhile  I  was  also  corresponding  with  Australian  entomolo- 
gists in  the  hope  of  procuring  specimens  of  a  Queensland  cane- 
infesting  leaf-hopper  for  comparison  with  ours;  1)ut  it  was  not 
till  some  six  months  after  I  began  this  correspondence  that  I  had 
the  great  satisfaction  of  receiving  from  Mr.  James  Clark  of 
Cairns,  four  specimens  of  this  Queensland  species,  which  proved 
to  be  the  same  species  as  our  own.  Mr.  Clark  also  informed  me 
that  tliis  leaf-hopper  had  been  known  there  for  years,  that  it  was 
their  only  species,  that  it  did  no  noticeable  damage  and  was  prob- 
ably kept  in  check  by  some  efficient  natural  enemy. 

As  I  have  mentioned  in  former  reports  the  fact  that  leaf-hop- 
per was  present  on  cane  in  Queensland  was  discovered  by  me 
when  inspecting  some  seed-cane  imported  from  that  country,  the 
said  seed-cane  containing  numerous  eggs  of  a  leaf-hopper,  while 
a  few  very  young  insects  were  also  present.  These  not  being 
at  a  stage  of  development  when  their  identity  with  our  own  species 


could  be  decided,  it  was  only  on  receipt  of  Mr.  Clark's  specimens 
that  this  was  finally   settled. 

GIiNKR.\L  ACCOUNT  OF  IIAPJTS  OF  TIIF  LEAF-HOPl'ER. 

3.  It  is  not  necessary  to  describe  at  great  length  the  habits  of 
the  leaf-hopper,  since  they  must  now  be  familiar  to  most  of  those 
concerned,'  and  at  one  time  or  another  I  have  already  fully  re- 
ported upon  these.  The  following  summary  may,  however,  be 
given.  The  eggs  are  laid  in  a  chamber  formed  by  the  ovipositor 
of  the  female  in  the  tissues  of  the  leaf  or  in  the  stem  of  the 
cane.  The  number  of  eggs  contained  in  one  of  these  chambers 
varies  considerably.  Lately  in  Hamakua  district  I  carefully  opened 
up  some  hundreds  of  these  chambers  and  found  the  number  of 
eggs  in  each  to  be  from  one  to  twelve  in  number.  That  end  of 
the  egg  which  is  nearest  the  external  surface  is  the  head  end  of  the 
future  leaf-hopper  and  the  red  pigment  spots,  which  form  the 
eyes  of  the  newly-emerged  insect,  are  conspicuous  at  some  dis- 
tance behind  the  narrow  apical  extremity  of  the  egg  before  it 
hatches.  In  the  leaves  the  eggs  are  deposited  on  either  surface 
of  the  thicker  parts,  and  being  of  elongate  form,  they  usually 
reach  about  half  way  through  the  tissues.  The  scar  is  always 
visible  and  is  often  covered  with  a  little  whitish  excretion.  The 
apex  or  head  end  of  the  eggs  is  generally  just  about  level  with 
the  surface  of  the  leaf,  but  sometimes  they  even  protrude  a  little 
from  the  orifice  of  the  chamber.  The  young  emerge  perpendicu- 
larly, head  first,  sometimes  two  together  from  the  chamber,  and  as 
they  emerge,  the  appendages  at  first  apparently  stuck  to  the  body 
become  free,  and  the  little  insect  is  at  once  active,  and  may  be 
seen  to  perform  peculiar  sidling  or  retrograde  movements  similar 
to  those  of  older  ones  or  of  the  adult.  As  a  number  of  individ- 
uals generally  hatch  from  a  single  chamber,  and  as  the  cham- 
bers are  extremely  numerous  in  a  single  leaf,  verv  many  being 
sometimes  present  in  a  square  inch  of  surface,  and  as  also  in 
stripped  cane  thousands  of  these  chambers  may  be  present  in  a 


single  stick,  the  total  number  of  leaf-hoppers  that  can,  and  some- 
times do,  emerge  from  a  single  stick  and  its  crown  of  leaves  is 
almost  incredible. 

The  young  when  they  hatch  are  of  a  sociable  nature  and  gre- 
garious and  especially  congregate  at  the  base  of  the  leaves,  and 
this  habit  is  also  largely  retained  by  the  adults,  which  often  also 
form  large  flocks  in  the  seclusion  of  the  youngest  leaves  of  the 
crown. 

It  is  in  the  immature  stages  while  growth  is  proceeding  that  the 
chief  damage  to  the  cane  is  done  and  the  great  excretion  of 
honey-dew  takes  place. 

It  is  not  necessary  to  trace  in  detail  the  development  of  the  in-^ 
sect  through  its  post-embryonic  stages  to  the  adult,  since  in  this 
j^oint  it  cscntially  agrees  with  the  several  other  island  Dclphacids. 
in  which  I  have  studied  these  points  and  presents  no  abnormal 
features. 

The  development  of  the  tegiiiina  and  wings  proceeds  in  the 
ustial  manner,  by  the  outgrowth  of  lobes  of  the  meso-  and  meta- 
thorax.  The  fully-winged  insect  is  capable  of  at  least  moderately 
extensive  flights,  as  is  shown  by  the  fact  that  it  is  attracted  by  the 
lights  of  steamers  at  some  distance  from  the  land,  and  on  land 
to  ligiits  very  far  removed  from  its  proper  haunts.  It  is  essen- 
tially nocturnal  in  its  activities  and  when  disturbed  in  the  day- 
time flies  but  a  short  distance,  or  is  even  unwilling  to  fly  at  all, 
trusting  to  its  leaping  powers  to  escape,  or  is  content  to  sidle 
round  the  leaf  or  stem  out  of  sight,  or  to  run  backwards  when 
threatened  from  the  front. 

The  male,  except  for  its  rather  smaller  bulk,  its  darker  abdo- 
men, and  dififerent  sexual  structures,  is  extremely  like 
the  female.  Copulation  takes  place  at  night.  The  adult  hoppers, 
most  of  which  lie  still  or  hidden  by  day,  emerge  in  crowds  from 
their  concealment  at  or  shortly  before  dark.  The  female  not 
rarely  lays  eggs  by  day,  but  probably  much  more  often  by  night. 
When  laying,  the  ovipositor  is  held  at  right  angles  to  the  ventral 
surface,  and  its  point  of  attachment  just  behind  the  posterior  legs 


10 

is  very  clearly  seen  when  the  tip  is  inserted  into  the  tissues  of  the 
leaf. 

BRACHYPTEROirs    OR    FLIGHTLESS    FORM    OF    THE    ADULT    LEAF- 
HOPPER. 

4.  At  certain  seasons  of  the  year,  in  certain  localities  at  least, 
and  perhaps  in  all,  a  distinct  form  of  the  leaf-hopper  appears,  dif- 
fering very  greatly  from  the  ordinary  adult.  This  fomi  is  remark- 
able for  the  fact  that  the  wings  are  so  little  developed  as  to  be 
unfit  for  flight  and  the  characteristic  markings  of  the  fully-winged 
individuals  are  lost.  Tn  fact,  no  one  at  first  sight  would  suppose 
the  short  and  long  winged  forms  to  belong  to  the  same  species, 
the  tegmina,  or  upper  wings,  of  the  former  not  extending  so  far 
back  as  the  tip  of  the  body,  while  the  lower  pair  are  aborted 
into  scarcely  visible  lobes. 

rolymorphism  in  the  development  of  the  wings,  aiTecting 
also  often  other  parts  of  the  body  is  a  well-known  feature  of  the 
Delphacid  leaf-hoppers,  and  may  be  seen  in  other  Hawaiian 
species.  This  appearance  of  a  single  species  under  two  or  more 
apparently  totally  distinct  forms  adds  greatly  to  the  difficulty 
of  the  student  in  determining  the  identity  of  these  leaf-hoppers. 

One  point  in  connection  with  this  flightless  form  is  worliiy  of 
notice.  Although  the  insect  has  not  been  with  us  for  study  for  a  suf- 
ficiently long  time  for  us  to^  speak  with  certainty  on  the  point,  yet,  so 
far,  the  worst  attacks  of  leaf-hopper  have  always  followed  or  been 
partly  coincident  with  the  production  of  these  flightless  females, 
that  is  to  say,  during  the  colder  months  of  the  year,  or  in  the 
early  summer.  Tn  the  course  of  mv  recent  tour  of  investigation 
through  Hamakua  to  Olaa,  T  did  not  find  a  single  example  of  the 
short-winged  form,  while  in  the  winter  months  from  some  plan- 
tations not  less  than  fifty  per  cent,  of  the  adults  sent  were  of  this 
form.  This  fact  and  some  observations  that  I  have  made  on  other 
Hawaiian  species,  lead  me  to-  believe  that  the  flightless  leaf-hop- 
pers are  more  prolific  than  the  fully  winged  specimens. 


11 


MIGRATORY    SWARMS    OF    THE    LEAF-HOPPER. 

5.  As  has  been  already  stated,  the  leaf-hopper  of  the  cane  is 
nocturnal  in  its  habits,  and  these  insects  are  not  seen  on  the  wing 
by  day  except  casually  or  when  disturbed.  On  certain  occasions, 
however,  they  have  been  seen  flying  in  one  direction  in  the  day 
time  m  such  numbers  as  to  form  a  migratory  swarm,  fjuite  like 
that  which  occurs  in  the  case  of  certain  locusts,  dragon-flies,  but- 
terflies and  other  insects.  1  am  not  aware  that  such  migrations 
have  been  recorded  previou,sly  of  leaf-hoppers,  but  they  are  known 
to  be  undertaken  by  the  somwhat  allied  group  of  Aphidac.  It 
would  appear  from  observations  made,  that  these  leaf-hopper 
migrations  are  largely  due  to  the  fact  that  the  food  supply  in  the 
place  whence  they  originate  has  become  exhausted  or  impover- 
ished by  the  number  of  the  insects. 

SIGNS    OF    LEAF-IIOPPER    ATTACK    AND    ITS    RESL  LTS. 

6.  \\'hen  leaf-hoppers  are  present  in  large  numbers  the  mid- 
rib and  sheath  of  the  leaf  often  become  conspicuously  red  either 
in  spots  or  almost  wholly,  but  such  an  appearance  may  be  due  to 
other  causes.  The  minute  discolored  scars  marking  the  opening 
of  the  egg  chambers  are  a  certain  sign  of  the  presence  of  the  in- 
sects, even  though  thc}^  may  not  themselves  be  noticed.  I  de- 
tected the  presence  of  the  pest  by  these  scars  (on  samples  of  cane 
sent  for  examination  for  other  reasons)  on  certain  plantations 
where  at  the  time  the  leaf-hopper  was  said  not  to  exist  at  all.  Like 
other  insects  of  their  sub-order,  leaf-hoppers  excrete  large  quanti- 
ties of  a  clear,  sweet  liquid,  called  honeydew,  and  on  this  the 
usual  fungi  grow.  Consequently  in  bad  attacks  whole  fields  of 
cane  may  be  black  with  the  usual  black  fungus,  or  in  striking 
contrast,  white  with  another  species,  or  the  black  smut  may  be 
followed  and  overgrown  with  the  white  fungus.  Either  of  these 
fungi,  however,  may  follow  bad  attacks  of  other  insects  that 
excrete  honeydew,  while  on  the  contrary,  bad  attacks  of  leaf-hop- 


12 

per  are  not  always  followed  by  a  very  large  fungus  growth,  for 
apparently  much  depends  on  climatic  conditions.  Very  heavy 
rains  sometimes  so  entirely  wash  off  the  hoiieydew  that  no  me- 
dium for  fungus  growth  remains.  These  fungi  necessarily  add 
to  the  damage  done  by  the  leaf  hoppers.  Though  they  send  no* 
hyphae  into  the  tissues  of  the  leaf,  yet  they  sometimes  entirely 
cover  these,  and  the  white  fungus  may  be  stripped  off  from  either 
surface  in  flakes  of  considerable  thickness,  forming  a  solid  shield 
against  light  and  air. 

The  result  of  leaf-hopper  attack  when  very  severe  is  seen  in 
ihe  drying  up  of  the  leaves  (from  the  constant  sucking  of  their 
juices)  before  their  full  functions  are  performed.  In  consequence 
of  this  the  joints  of  the  stem,  even  at  the  time  when  they  should 
be  thickening,  become  on  the  contrary  tapering  and  contracted,  so 
much  so  sometimes  that  the  crown  topples  over  and  is  even  en- 
tirely destroyed,  further  growth,  of  course,  being  at  an  end. 
Young  cane  is  sometimes  entirely  killed  out  before  any  consid- 
erable length  of  stem  has  been  produced. 

Although  total  destruction  of  a  plant  only  occurs  when  the  leaf- 
hopper  is  in  the  most  excessive  numbers,  yet  even  when  present 
in  large  num1)ers  the  injury  done  must  be  considerable.  Should 
a  plantation,  thus  attacked,  after  all  produce  a  crop  that  comes  up 
to  the  estimates,  yet  it  is  safe  to  say  that  without  the  pest  these 
would  be  largely  exceeded. 

REL.\TIVE  IMiVIUNITY  OF  DIFFERENT  VARIETIES  OF   CANE  FROM 
ATTACK. 

7.  Some  varieties  of  cane,  other  things  being  equal,  appear 
less  subject  to  attack  than  others.     It  must  not  be  for  a  minute 


*0f  course  reference  is  here  made  only  to  the  fungi  whicli  usually  fol- 
low the  attacks  of  Homoptera.  Several  species  of  true  leaf  parasites  .ire 
found  in  the  cane-fields  and  appear  now  to  be  more  than  usually  dis- 
seminated, possibly  owing  to  the  abundance  of  leaf-hoppers  and  insects 
accompanying  them,  that  carry  the  spores.  These  fungi  so  far  as  I  have 
examined  them  appear  all  to  be  known  in  other  countries  and  are  prob- 
ably importations  into  Hawaii. 


13 

snpposerl  that  were  a  plantation  formed  entirely  of  one  of  these 
more  inmiune  varieties  it  would  necessarily  escape  with  little  or 
no  damage.  The  mere  fact  that  the  leaf-hopper  will  attack  gram- 
inaceous plants  other  than  cane  (in  the  absence  of  the  latter)  is 
sufficient  proof  that  such  is  not  likely  to  be  the  case,  for  there 
are  naturally  much  greater  differences  between  these  and  cane 
than  between  the  most  different  varieties  of  the  cane  itself.  Rel- 
ative immunity  from  attack  is  a  most  difficult  matter  to  judge 
of,  because  one  can  never  be  sure  how  much  immunity  is  due  to 
the  nature  of  the  variety  of  cane  and  how  much  to  other  causes. 
Even  in  a  field  of  cane  of  one  variety  and  apparently  similar  in 
growth,  one  can  frequently  see  the  capriciousness  of  the  leaf- 
hopper  in  its  attacks  (a  capriciousness  notorious  too'  in  other  in- 
sects) from  the  fact  that  certain  spots  are  more  badly  attacked 
than  others.  In  some  cases  this  is  no  doubt  due  to^  causes  that 
can  be  perceived  by  man,  such  as  greater  shelter  from  prevalent 
winds,  a  ranker  growth  of  leaf,  presumably  affording  more  abund- 
ant juice  for  food,  but  in  other  cases  no  adequate  cause  for  this 
capriciousness  is  apparent. 

It  seems  certain  that  some  varieties  of  cane  will  stand  the 
attack  of  leaf-hopper  better  than  others.  Mr.  Eckart,  Director  of 
the  Hawaiian  Sugar  Planters'  Experiment  Station,  has  furnished 
me  with  a  list  of  new  varieties  of  cane  (see  Appendix,  Note  II 
below),  grown  there,  arranged  in  order,  according  to  the  relative 
injury  that  each  sustained  from  leaf-hopper. 

There  may  come,  however,  so  severe  an  attack  that  no  cane  can 
resist  it  Thus  we  have  seen  plants  of  "Yellow  Caledonia"'  (at 
the  extreme  end  of  the  list)  which  were  of  the  strongest  and  most 
thrifty  nature  previous  to  the  attack,  some  entirely  destroyed  and 
others  very  badly  injured  after  a  bad  outbreak.  It  is,  however, 
probable  that  from  an  attack  of  hopper  which  would  entirely  de- 
stroy a  field  of  ''Rose  Bamboo,"  for  instance,  a  field  of  "Yellow 
Caledonia"  might  recover. 


14 

MODE  OF  OCCUPATION  OF  NEW  FIELDS  IN  A  DISTRICT  WELL  OC- 
CUPIED   BY    LEAF-HOPPERS, 

8.  When  a  field  of  cane  is  first  occupied  by  leaf-hoppers  they 
sometimes  appear  to  spread  over  this  m  a  very  uniform  manner, 
provided  always  that  the  conditions  of  growth  of  the  cane,  shel- 
ter, &c.,  are  uniform.  This  can  sometimes  be  very  well  seen  in 
fields  of  very  young  cane.  One  that  was  examined  by  me  con- 
sisted of  cane  about  one  month  above  ground,  and  on  the  aver- 
age eacli  plant  was  the  home  of  two  mature  leaf-hoppers.  Obvi- 
ously these  had  migrated  thither  from  adjoining  fields,  as  they 
could  not  have  reached  maturity  on  such  young  plants. 

Two  fields  of  cane  adjoining  one  another,  one  of  Yellow  Cale- 
donia, the  other  of  Rose  Bamboo  variety,  each  about  five  months 
old  held  a  stock  of  20-50  adult  hoppers  to  each  crown,  uniform- 
ly distributed  in  either  field.  These  also  had  come  by  migration., 
for,  at  the  time,  there  were  very  few  young  in  these  fields,  and 
the  egg  chambers  nearly  all  contained  unhatched  eggs.  This  uni- 
form distribution  of  hoppers  over  new  fields,  of  course,  only  ap- 
plies to  such  districts  as  have  already  in  some  parts,  at  least,  a 
superabundant  supply  of  the  pest.  Their  first  appearance  in  a 
district  has  (so  far  as  such  early  and  exact  evidence  as  I  have  on 
tlic  subject  goes)  generally  been  limited  to  a  quite  small  area  of 
one  plantation. 

ON  STRIPPING  CANE  IN  LEAF-HOPPER  ATTACK, 

f 

9.  As  I  have  incidentally  mentioned,  leaf-hoppers  like  the 
more  sheltered  spots  and  hence  it  can  sometimes  be  seen  that  they 
are  in  less  numbers  in  well  stripped  fields  than  in  those  that  are 
not  stripped.  This  probably  means  nothing  more  than  that  the 
total  number  of  the  insects  present  are  more  unevenly  distributed 
than  would  be  the  case  were  all  fields  stripped.  Probably  not  many 
of  the  pest  are  destroyed  by  stripping,  since  most  of  the  eggs  laid 
in  such  leaves  as  are  stripped  have  already  hatched,  and  those 


15 

which  have  not  will  produce  young  after  the  leaves  are  removed, 
as  I  have  myself  proved. 

Fields  of  unstripped  cane  that  already  contain  leaf-hopper  in 
such  numbers  as  to  be  doing  considerable  damage,  are  better  left 
in  that  condition,  because  a  large  proportion  (in  fact  most)  of  the 
eggs  and  pupae  of  some  of  the  most  active  of  its  enemies  are  to 
be  found  attached  to  the  old  dead  or  half-dry  leaves,  and  some  of 
these  enemies  are  more  intolerant  of  exposure  by  stripping  than 
are  the  leaf-hoppers  themselves. 

DIFFERENCE   IN    SEVERITY   OF   LEAF-IIOPPER  ATTACK   ON   NEIGHUOR- 
ING    PLANTATIONS 

10.  In  some  cases  it  is  evident  that  neighboring  plantations 
have  suiTered  from  the  attack  of  leaf-hopper  in  a  very  diiferent 
degree.  This  is  due  to  several  causes  and  sometimes  obviously 
(i)  to  the  difference  in  the  length  of  time  that  the  leaf-hopper  has 
been  present  in  large  numbers.  Thus  a  limited  area  in  a  district 
becomes  first  badly  infected  and  when  this  spot  has  produced  a 
superabundant  supply  of  the  pest,  it  spreads  (sometimes  in  a 
migratory  swarm)  over  a  much  larger  adjoining  area,  which  suf- 
fers greatly,  while  the  cane  immediately  adjoining  this  larger  area 
is  not  much  injured.  (2)  Slightly  different  climatic  causes 
probably  exert  a  restraining  influence  or  the  reverse.  (3)  In 
some  cases  the  number  of  natural  enemies  of  the  leaf-hopper  (es- 
pecially the  numbers  present  when  first  it  has  occupied  a  new 
locality)  may  turn  what  threatens  to  be  a  bad  outbreak  into  a 
light  attack.  In  some  cases  the  fact  that  on  adjoining  plan- 
tations the  seriousness  of  the  attack  diifers  greatly  seems  inexplic- 
able, and  due  only  to  that  apparent  capriciousness  of  the  insect, 
of  which  I  have  already  spoken. 

Some  eight  months  ago  I  wrote  in  my  report,  "There  is  little 
doubt  that  its  destructiveness  will  vary  very  much  with  the  lo- 
cality and  according  to  the  season  and  it  is  by  no  means  certain 
that  it  has  as  yet,  even  on  Oahu,  multiplied  to  the  fullest  extent.'' 
Later  observations  have  fully  convinced  me  of  the  truth  of  these 


16 

statements,  and  I  would  add  that  were  the  pest  allowed  to  mill-' 
tiply  unchecked  by  natural  enemies,  it  is  by  nO'  means  necessarily 
the  plantations  which  hitherto  have  suffered  most  that  would  do 
SO  in  other  seasons,  nor  those  which  have  escaped  considerable 
damage  this  year,  that  would  be  exempt  another  year. 

NATURAL    ENEMIES    OF    THE    LP^AF-HOPrER    ALREADY    PRESENT 
IN    THIS    COUNTRY. 

II.  During-  my  recent  journey  through  Hawaii,  very  careful 
examination  was  made  as  to  the  status  of  all  the  insects  present 
in  the  cane-fields  in  connection  with  the  leaf-hopper  attack.  Some 
of  these  are  direct  enemies  of  the  hopper,  others  are  attracted 
b\-  the  exudations  of  the  injured  cane  or  the  fungoid  growths, 
wliile  others  are  parasites  of  some  of  the  foregoing. 

The  natural  enemies  that  I  observed  to  be  present,  and  their 
parasites,  were  the  chief  source  of  interest  on  this  journey,  be- 
cause attention  to  the  former  might  naturally  give  some  infor- 
mation as  tO'  what  we  might  look  to  for  aid  in  other  countries, 
while  a  consideration  of  the  parasites  here  present  would  influ- 
ence one's  choice  in  the  selection  of  such  natural  enemies  as  it 
may  be  advisable  to  import. 

I  will  now  enumerate  the  most  important  species  of  insects  or 
other  creatures  present  in  infected  cane-fields  in  connection  with 
leaf-hopper  attack.  The  habits  of  a  few  of  these  are,  I  regret  to 
say,  not  yet  accurately  determined,  the  time  at  my  disposal  on  my 
journey  throug-h  Hawaii  being  insufficient  for  examining  into 
some  of  the  most  obscure  species.  Those  which  seemed  of  pri- 
mary importance  were,  however,  for  the  most  part  fully  investi- 
gated. 

(a)     The  Block-Spotted  Red  Lady-Bird  (Cocciiiella  repanda.) 

One  enemy  of  the  leaf-hopper  is  ubiquitous  or  nearly  so 
throughout  the  cane-fields  and  in  many  parts  extremely  numerous. 
This  is  the  red,  black-spotted  lady-bvrd  {Coccinella  repanda) , long 


17 

since  imported  into  the  islands  by  Koebele.  Natuarally  an  Aphis- 
eater,  it  is  taking  quite  kindlv  to  feeding  on  the  young  leaf-hopper. 
The  beetle  itself  probably  does  not  do  much  execution,  but  the 
larva  is  very  efficient  on  the  young,  especially  at  the  moment  when 
tiiey  emerge  from  the  eggs,  and  in  their  younger  stages,  and  also 
is  able  sometimes  to  obtain  the  eggs  themselves. 

In  some  fields  of  young  cane,  where  the  leaf-hoppers  were  all 
adult,  or  only  very  few  young  arc  to  be  found,  this  lady-bird  was 
either  absent  or  in  very  small  numbers.  The  reason  is  olndously 
because  they  are  not  greatly  attracted  until  the  young  leaf-hop- 
pers appear,  since  these  are  the  chief  food  of  the  lady-bird's  larva. 

In  Hamakua,  some  fields  of  young  cane,  where  young  leaf- 
hoppers  were  already  very  numerous,  were  estimated  on  June  21st 
to  have  three  adult  lady-birds  to  each  stool  on  the  average,  and 
very  often  several  larvae  of  the  same  in  addition,  as  well  as  nu- 
merous eggs. 

(aa)     Bracouid  Parasite  of  Coccinclla  Repanda. 

Most  unfortunately  an  enemy  of  this  lady-bird  is  already  in  the 
jield  and  generally  distributed,  though  not  yet  very  numerous.  It 
is,  so  far  as  is  known  to  me,  the  onl};  lady-bird  parasite  at  present 
found  in  these  islands  and  probably  came  from  America  at  the 
same  time  that  the  one  foreign  lady-bird,  that  was  found  here  prior 
to  Koebele's  importations,  was  brought  (accidentally)  to  this 
country.     This  parasite  is  the  Cciillsfcs  auiericana  of  Riley. 

This  parasite  was  known  to  me  in  1892  as  attacking  Ncda  ab- 
uoiui)ialis,  some  time  before  the  Coccinclla  above  mentioned  was 
introduced,  but  now  it  seems  chietlv.  if  not  entirely,  to  attack  the 
latter.  It  was  found  generally  distributed  over  windward  Ha- 
waii and  more  numerous  in  proportion  to  the  number  of  its  host 
in  parts  of  Hilo  than  in  Hamakua.  Several  times  the  female  of 
the  parasite  was  seen  grappling  with  and  curled  around  the  ma- 
ture lady-bird  in  which  it  was  laying  an  egg,  and  the  dead  and 
dying  beetles  could  be  found  in  some  numbers  any  day  in  many 


cane-fields.  Long  after  the  emergence  of  the  larva  ol  the  parasite 
from  the  interior  of  the  lady-bird  and  after  it  has  completed  its 
cocoon,  the  mifoi"tunate  beetle  still  shows  signs  of  life  in  the 
spasmodic  twitching  of  its  legs. 

(b)  Scyiunns  and  Cryplolaernus. 

Tlie  other  lady-l)irds  noticed  in  the  cane-fields  are  the  Platyo- 
?nus,  fin  small  numbers  locally),  the  Cryptolaemns  (common  lo- 
cally) and  the  small  Scynmus  -rhndus  (common  locally).  The 
first  named  was  never  seen  to  attack  leaf-hopper  and  was  no  doubt 
attracted  by  Aphis,  its  usual  food.  The  Crypfolaemits  had  been 
evidently  attracted  by  mealy-bug,  which  was  common  on  the  roots 
and  stems  of  a  grass  growing  in  the  cane-fields.  Having  de- 
molislied  these  the  larvae  of  this  lady-bird  were  starving  and  wan- 
dering over  the  cane  in  search  of  foo'd,  and  in  several  instances 
were  seen  to-  kill  and  eat  the  young  leaf-hoppers.  The  Scyiunus 
larva  w^as  also  seen  to  attack  the  young  hoppers.  Neither  of 
these  species  were,  however,  to  be  compared  with  the  larva  of 
the  CoccuicUa^  either  in  numbers  or  effectiveness  as  destroyers 
of  leaf-hoppers. 

(c)  Tlic  Lacc-Whiiy  Fly  {Chrysopa  micro phya.) 

Though  I  have  enumerated  elsewhere  30  species  of  Hawaiian 
knee-wings,  only  the  one  above  mentioned  was  found  in  the  cane- 
fields. 

The  larva  of  this  lace-wing  fly  is  an  excellent  enemy  of  the 
leaf-hopper  in  the  taller  cane.  In  the  young  cane  these  larvae 
are  absent  or  scarce,  because  this  aft'ords  indifferent  shelter  to  the 
delicate  fly.  They  are  also  very  much  more  numerous  on  some 
plantations  than  others,  though  present  in  all  that  were  visited. 
vSeveral  of  the  flies  and  their  larvae  may  in  places  be  seen  on 
nearly  every  stool  of  cane  and  the  eggs  and  puparia  were  every- 
where, especially  on  old,  unstripped  leaves.  The  lace-wing  larva 
is  not  only  able  to  destroy  the  young  leaf-hoppers,  but  was  also 


seen  to  obtain  the  eggs,  its  long-pointerl  jaws  being  well  adapted 
for  such  work. 

(cc)     HciinlcUnc  Parasite  of  the  Chrysol^a. 

The  lace- wing-  fly  has  also  its  parasite,  in  the  shape  of  an  ich- 
neumon fly,  wliich  was  seen  laying  its  eggs  in  the  pupa  of  this 
useful  insect.  I  am  inclined  to  think  that  this  parasite  is  always 
comparatively  rare  and  is  not  likely  to  become  common  enougli 
to  check  the  production  of  the  lace-wings,  but  time  alone  can 
prove  this.  This  parasite  was  seen  in  the  most  diverse  locali- 
ties, but  always  singly. 

(d)  Ncsojiiicronnis  z'agiis  (Hcincrobiidac) . 

This  insect  was  fairly  common  in  several  Iccalities  on  the  af- 
fected cane.  Its  larva  was  not  found  and  hence  there  is  uncer- 
tainty as  to  its  food".  It  is  possible  that  it  was  living  ou  the  mi- 
nute Psocidac,  which  browse  on  the  black  fungus  which  grows  on 
the  excretions  of  the  leaf-hopper,  and  not  on  the  latter.  As  no 
Aphis  or  other  likely  food  was  present  it  could  only  have  been 
l^red  at  the  expense  of  one  or  other  of  these. 

(e)  Rcdiiviolus  blackbunii,  a  predatory  native  bug. 

This  narrow  pale-colored  bug,  A\as  noticed  in  various  localities, 
but  not  very  commonly.  It  preys  on  the  young  of  the  leaf-hop- 
per and  no  doubt  on  other  small  insects  affecting  or  frequenting 
tlie  cane,  and  it  also  sucks  up  the  sweet  excretion  of  the  leaf- 
hopper.  Another  species,  R.  lusciosits,  was  seen  in  the  Olaa 
cane-lields,  but  was  not  seen  to  attack  the  leaf-hoppers. 

(f)  Natiz'c  Pciitatouiid  Bug   (Oec/wJia  grisca). 

In  !arge  numbers  in  some  localities,  but  especially  in  fields  in 
the  neighborhood  of  native  forest.  The  young  were  repeatedly 
seen  sucking  the  juices  of  mature  leaf-hoppers,  but  the  fully  de- 
veloped bugs  usually  feed  on  caterpillars  and  larger  insects. 


20 

(g)     Zcitis  pcregrinus  {Imported  Rediiviid  bug). 

In  ni}'  earliest  reports  I  called  attention  to  the  efficiency  of  this 
bug  as  a  destroyer  of  leaf-hopper  and  at  the  same  time  mentioned 
its  demerits,  as  it  is  also  a  destroyer  of  highly  beneficial  insects. 
This  bug  was  first  seen  as  a  great  rarity  in  the  Government 
Nurser}-  in  1897.  By  1900  it  had  become  common  and  soon 
spread  generalh'  over  Oahu,  increasing  very  rapidly  in  cane- 
fields  affected  by  leaf-hopper.  Excepting  possibly  Kauai,  it  is  now 
found  on  all  the  islands.  Both  the  young  and  mature  bug  feed 
on  the  leaf-hoppers  and  they  seek  these  when  hidden  at  the  bases 
of  the  leaves  as  well  as  in  the  open.  Not  infrequently  we  mav  see 
this  bug  with  its  beak  thrust  into  the  body  of  a  CoccineUa,  but  in 
the  canc-ficlds  at  the  present  time  it  is  clearly  feeding  chiefly  on 
the  leaf -hopper. 

(h)     Small  Bug  of  Fain.  Anthocoridac. 

I  have  not  been  able  to  determine  the  species  of  this  minute 
and  obscure  bug.  which  exists  in  great  numbers  in  badly  affected 
cane  in  some  localities,  and  is  rare  or  absent  in  others.  It  is  of 
nocturnal  habits  apparently  and  secretes  itself  during  the  day- 
time m  the  same  way  and  places  as  do  young  leaf-hoppers.  I 
have  very  little  doubt  that  it  preys  on  these,  ior  the  small  Antho- 
corids  are  notoriously  great  destroyers  of  other  small  insects.  Its 
extraordinary  profusion  in  some  samples  of  badly  affected  cane 
leads  me  to  suspect  that  it  will  prove  of  great  importance,  and  it 
is  rapidly  extending  its  range  and  will  soon  be  ubiquitous. 

(i)      Hymcnoptcron.s  Parasite  of  the  Leaf-Hopper.    (Ecthrodcl- 
pliax  fairchildii. 

Appended  to  th.is  report  (Note  III)  will  be  found  a  technical 
description  of  an  external  hymenopterous  parasite  of  the  leaf- 
hopper,  and  one  which  is  a  very  efficient  enemy  in  some  localities 
and  will  shortly  be  spread  over  the  whole  islands. 

This  interesting  parasite  was  first  submitted  to  me  by  Mr.  G, 


21 

Fairchild  and  I  have  named  it  specifically  after  him.  There  is 
no  doubt  that  this  parasite  has  transferred  its  attack  from  one  or 
more  of  the  native  Delphacid  leaf-hoppers  to  the  imported  species. 
I  have  long  suspected  the  Hawaiian  species  of  Gonatopus  to  be 
parasitic  on  leaf-hoppers  and  this  supposition  is  greatly  strength- 
ened by  the  fact  that  the  new  and  allied  form  of  parasite  is  so. 
External  parasitic  larvae  on  native  leaf-hoppers  were  found  by 
me  many  years  ago  on  Hawaii,  but  I  was  unable  to  rediscovei 
them  on  my  recent  hurried  trip,  the  old  locality  having  been 
spoilt,  owing  to  the  total  destruction  of  the  forest.  Could  the 
Gonatopus  be  collected  in  some  numbers  and  transferred  to  the 
cane-fields  I  suspect  it  would  attack  the  leaf-hopper,  as  does  the 
parasite  now  imder  consideration.  The  Gonatopus,  being  wing- 
less, has  not  the  same  facility  for  transferring  its  attack  to-  the 
cane  leaf-hopper  as  has  the  winged  Ecthrodelphax.  I  may  add 
that  I  believe  there  is  at  least  one  other  hymenopterous  parasite 
on  the  native  Dephacids  of  the  forest. 

To  return  to  the  Ecthrodelphax,  it  is  always  the  young  of  the 
leaf-hopper  that  is  attacked,  and  a  single  hopper  may  sustain 
either  one  or  two  parasites.  These  are  nearly  always  lodged  be- 
neath the  lobes  which  develop  into  the  tegmina,  or  upper  wings ; 
one  on  each  side  of  the  body,  when  two  parasites  are  present  in 
tlie  same  host. 

The  parasite  appears  externally  as  a  small,  nearly  circular,  im- 
pressed black  object  adherent  to  the  young  leaf-hopper.  The  lat- 
ter seems  to  be  hardly  inconvenienced  by  the  parasite,  remaining 
as  active  and  plump  as  the  non-parasitized  individuals. 

After  a  Lime,  however,  (always  shortly  before  the  full  growth 
of  the  parasitic  larva )  the  hopper  becomes  sluggish  and  then  en- 
tirely stationary.  This  may  happen  either  shortly  before  or  not 
till  some  time  after  the  black  shell-like  covering  of  the  parasite 
splits  by  a  longitudinal  (mediodorsal)  fissure  and  exposes  the  back 
of  the  white  maggot  wathin.  This  torpidity  of  the  leaf-hopper 
and  the  splitting  of  the  covering  of  the  parasite  is  almo^st  certainly 
the  outward  sign  of  a  change  of  habits  in  the  parasite  (probably 


22 

coinci'lent  with  a  moult  and  change  of  form  of  the  latter).  From 
this  time  until  the  hopper  dies  and  the  maggot  finally  quits  hold  of 
its  prey  the  sight  as  examined  under  a  lens  forms  one  of  the  most 
repulsive  sights  that  natural  history  can  afford. 

Soon  after  the  splitting  of  the  hlack  covering  and  the  exposure 
of  the  white  maggot,  a  conspicuous  change  takes  place  in  the 
colour  of  the  latter,  it  becoming  pink  or  reddish.  No  doubt  the 
maggot,  which  has  hitherto  fed  delicately  without  doing  any 
vital  injury  to  its  host,  now  proceeds  to  ingest  the  contents  of  the 
hopper  in  an  indiscriminate  manner,  and  the  change  in  color  is 
clearly  due  to  this.  If  removed  at  this  time  from  the  hopper  it  is 
seen  to  have  very  mobile  and  hard  (chitinized)  mouth  parts,  while 
the  thin  and  collapsed  black  covering  still  adheres  some  distance 
behind  the  head.  Growth  is  extremely  rapid  and  the  simultaneous 
shrinking  of  the  hopper,  as  its  contents  are  absorbed  by  the  para- 
site, enhances  this  effect.  Thus  when  the  splitting  of  the  black 
covering  takes  place  the  hopper  may  be  three  or  four  times  the 
size  of  the  parasite,  when  the  latter  is  full  fed  the  proportions  may 
be  exactly  reversed.  The  removal  of  the  contents  of  the  hopper 
can  be  easily  seen  through  parts  of  the  cuticle.  Generally  early  in 
the  proceedings  the  soft  contents  of  one  or  both  eyes  and  of  the 
head  are  seen  to  be  in  rapid  motion,  like  a  boiling  fluid ;  suddenly 
all  the  pigment  is  removed  from  one  eye  (usually  the  one  on  the 
opposite  side  to  the  parasite)  and  it  becomes  an  opaque  white 
spot,  then  the  other  is  often  similarly  destroyed,  or  sometimes 
both  more  or  less  sinudtaneously. 

Finally  the  maggot,  when  it  has  finished  feeding  withdraws  its 
head,  and  may  then  some  times  be  seen  busily  engaged  in  apply- 
ing sticky  matter  from  its  mouth  to  its  body.  Its  surface  thus 
becomes  strongly  adhesive  and  when  it  quits  its  prey,  it  is  able 
(though  of  course  quite  legless)  to  crawl  freely  over  any  surface 
iiowever  smooth.  Soon  it  spins  a  neat  white  cocoon,  from 
which  it  emerges  as  an  active  winged  insect  in  about  i8  days. 


23 

(j)     Various  Species  of  Earivigs   {ForHcuIidae),  Etc. 

Four  species  of  earwigs  in  all  have  been  found  on  the  cane 
plants,  the  particular  species  in  any  one  field  generally  depending 
on  the  nature  of  the  locality.  Of  these  four  species  two  have  been 
actually  seen  to  destroy  the  leaf-hopper,  and  there  is  very  little 
doul)t  that  the  others  do  so  also.  Further  it  is  probable  that  one 
or  two  other  species  of  earwigs  could  be  found  were  all  the  cane- 
fields  to  be  thoroughly  investigated.  The  species  collected  by  my- 
self in  badly  affected  cane-fields  are  Anisolahis  ainiulipcs^  Labia 
pygidiata,  Labia  fspf,  and  Chelisochcs  nwrio.  No  doubt  the  ear- 
wigs are  always  present  in  the  cane  in  some  numbers  whether  leaf- 
liopper  be  present  or  not,  and  I  do  not  suppose  that  thev  are  of 
any  great  importance  in  this  connection.  The  same  may  be  said 
of  the  green  cricket  (Xipliidiimi)  which  will  eat  leaf -hoppers  vo- 
raciously in  confinement  and  certainly  does  so  to  some  extent  in 
the  field,  while  it  also  feeds  on  the  leaves  of  the  cane,  which  are 
no  doubt  its  chief  food. 

(k)     yiiifs  {V avians  species). 

At  certain  times  ants  kill  considerable  numbers  of  young  leaf- 
h(5ppers,  while  at  other  times  if  they  do  not  actually  protect  them 
from  their  enemies  they  certainly  do  not  harm  them.  When  the 
hoppers  are  excreting  an  abundance  of  honey-dew  I  believe  the  ants 
rarely  or  never  interfere  with  them,  since  they  prefer  this  sweet  ex- 
cretion to  the  hoppers  themselves.  In  order  to  determine  which 
species  of  ants  would  kill  the  young  leaf-hoppers,  only  such  in- 
dividual ants  as  were  actually  seen  to  kill  these  in  the  field  were 
collected  by  me.  The  following  species  form  the  collect i ou  : 
Tapinoiiia  melanocephala,  Preuolepis  bourbonica,  Pheidole  meg- 
acephala,  Jetramorioruin  gnineense,  Cardiocondyla  Wroughiomi 
and  Mo'.oiiwriiim  floricola. 

(1)      Probable  Dipterous  Parasite. 

I  include  here  vv'Hi  some  Houbt  a  native  species  of  Pipiiiiculiis 


2-1 

observed  in  some  numbers  in  some  cane-fields  and  certainly  breed- 
ing there. 

I  have  frequently  observed  these  flies  in  the  forests  of  several 
islands  where  leaf-hoppers  are  abundant,  but  never  in  the  long 
course  of  my  collecting  have  T  previously  found  them  in  the  cane- 
fields  or  outside  the  forest.  As  it  is  knoAvn  that  insects  of  this 
group  are  parasitic  on  leaf-hoppers,  it  is  highly  probable  that 
the  species  observed  by  me  in  fields  attacked  by  the  cane-leaf- 
hopper  are  parasitic  on  this  species.  This  species  of  PipHiiculus 
appears  to  be  undescribed,  though  very  close  to  the  P.  iiigrofarsa- 
tiis,  collected  by  me  in  the  Kona  forests. 

(m)     Sl'idcrs  of  Many  Species. 

Tn  my  early  reports  I  called  attention  to  tlie  large  number  of 
spiders  generally  found  in  the  cane-fields,  and  there  is  no  doubt 
tliat  owing  to  the  abundance  of  food  furnished  b)-  the  leaf-hoppers 
these  have  in  some  localities  multiplied  to  an  extraordinary  degree. 
Fully  twenty  species  of  diverse  families  are  knowai  to  me  to  fre- 
quent the  cane-fields,  a  large  proportion  of  these  being  imported 
species.  The  species  most  numerous  on  one  plantation  are  often 
extremely  dififerent  from  those  on  another.  Thus  in  one  locality 
it  is  a  common  Tctragnatha,  in  another  a  species  of  Cyclosa  or 
Argiope,  in  another  an  Attid  or  Thomisid,  that  most  abounds;  in 
general  two  or  three  forms  are  abundant  on  a  single  plantation. 
I  believe  the  species  that  hunt  their  prey  without  the  use  of  webs 
are  far  more  effective  against  leaf-hoppers  than  those  that  spin 
these.  To'  what  extent  the  multiplication  of  individuals  has  pro- 
ceeded in  parts  of  some  plantations  may  be  judged  from  the  fact 
that  as  many  as  50  nests  of  one  single  species  of  spider  have  been 
counted  on  a  single  leaf.,  and  each  of  these  nests  will  probably  con- 
tain from  40  to  50  eggs  on  an  average. 

(mm)     Parasite  of  Spiders. 

Some  of  the  most  eft'cctive  species  of  spiders  are  themselves  not 
exempt  from  attack.    Thus  a  Cryptic  Ichneumon  pierces  the  cov- 


ering  of  the  nest  and  lays  a  few  eggs  amongst  those  of  the  spider. 
Two  or  three  of  the  resulting  larv^ae  are  sufficient  to  entirely  de- 
stroy every  egg  in  the  spider's  nest,  from  which,  instead  of  scores 
of  young  spiders,  there  usually  emerge  two  or  three  specimens 
of  the  parasite.  This  parasite  is  widely,  if  not  generally  distrib- 
uted, but  where  it  was  most  common  not  more  than  5  per  cent,  of 
the  spiders'  nests  were  destroyed  at  tlie  time  of  my  visit  to 
Hawaii. 

(n)     Finigi  Parasitic  011   the  Lcaf-Hoppcr. 

Several  species  of  fungus  are  well  known  to  attack  the  native 
leaf-hoppers  in  certain  localities  and  t\\  O'  or  three  of  these  have,  as 
mi  gilt  have  been  expected,  transferred  their  attack  to  the  sugar- 
cane species,  while  others  have  not  yet  done  so.  In  1892  a  con- 
siderable mortality  amonst  native  leaf-hoppers,  caused  by  one  of 
these  fungi,  was  noticed  in  parts  of  Kona  district  and  subse- 
quently Koebele  and  myself  found  leaf-hoppers  killed  in  the  same 
maimer  in  Olaa. 

riiese  diseases  are  very  noticeable  amongst  the  cane  leaf-hoppers 
in  Olaa,  though  comparatively  a  very  small  percentage  of  the 
hoppers  present  were  affected  at  the  time  of  my  visit.  Probably 
with  more  rainy  weather  (at  the  time  of  my  visit  it  was  extreme- 
]}•  -Jiy)  diese  fungi  would  be  more  active  agents  in  destroying 
the  pest.  It  should  be  noticed  that  at  the  time  when  I  made  my 
oi^servations,  it  was  the  mature  leaf-hoppers,  almost  invariably, 
that  were  attacked,  and  if  this  proves  to  be  usually  the  case,  the 
value  of  these  fungi  will  be  greatly  diminished,  since  the  leaf- 
hopper  does  mo.st  damage  before  becoming  mature,  and  further, 
of  those  killed  a  considerable  proportion  may  already  have  laid 
their  eggs. 

The  evidence  of  disease  is  manifest  in  the  hoppers  before  actual 
death  takes  place.  The  infected  insect  is  slow  and  lethargic  and 
finally  stations  itself  on  the  under  side  of  the  leaf  in  the  open, — 
that  is  to  say.  it  generally  leaves  its  concealment  at  the  base  of  the 
leaf  or  elsewhere  and  moves  for  a  longer  or  shorter  distance  to- 


20 

wards  the  tip.  After  a  time  the  filaments  or  hyphae  of  the  fungus 
grow  out  from  the  inside  of  the  insect  on  the  ventral  surface  and 
attach  it  to  the  leaf.  Finally  special  hyphal  outgrowths  on  which 
the  spores  are  produced,  are  formed  over  the  rest  of  the  surface. 
Even  after  death  during  the  early  stages  of  fungus  growth,  the  hop- 
pers appear  perfectly  natural,  and  without  close  examination  it  is 
not  always  possible  to  be  sure  whether  the  insect  is  really  dead  or 
merely  resting  on  the  leaf.  At  present  we  cannot  judge  of  the 
effectiveness  of  these  fungus  diseases,  because  there  has  been  no 
special  investigation  as  to  their  prevalence,  and  the  percentage  of 
leaf-hoppers  killed,  at  the  various  seasons  of  the  year.  As  has 
been  mentioned,  at  the  time  I  looked  intO'  the  matter,  the  condi- 
tions were,  in  my  opinion,  unfavorable  for  the  spread  of  such  dis- 
eases, owing  to  the  climatic  conditions.  It  may  be  said,  however, 
that  in  Olaa,  and  no  doubt  in  some  few  cane-growing  districts  be- 
sides, conditions  are  as  a  rule  cxceptioiially  favorable  for  the  growth 
of  entomophthorous  fungi,  as  is  evidenced  by  the  large  mor- 
tality amongst  insects  of  all  kinds  from  such  parasites.  Caterpil- 
lars, moths,  beetles,  cockroaches,  may  be  easily  found  killed  by 
theiu,  and  the  variety  of  the  destroyers  themselves  is  consideralile. 
Since,  however,  in  most  localities,  even  in  the  wet  mountains,  such 
attacks  are  comparatively  rare  or  rarely  noticed,  it  is  hardly  prob- 
able that  these  fungi  which  destroy  the  leaf-hoppers  could  be  estab- 
lished in  the  localities,  still  less  favorable  for  fungus  growth,  that 
are  occupied  by  most  cane-fields. 

INSECTS  rRESr':NT  TN  THE  AFFECTED  CANE  FIELDS  THAT  INCREASE 
THE  INJURY  DONE  RY  LEAF-TIOI'PER,  AND  BUT  FOR  THE  PRES- 
ENCE OF  THE  LATTER  WOULD  I!E  EITHER  AliSENT  OR  FAR  LFSS 
NUMEROUS. 

12.  It  would  not  be  proper  to  pass  entirely  unnoticed  the 
large  number  of  insects  attracted  to  the  hopper-aifected  cane. 
Though  they  have  no  effect  on  the  leaf-hopper  itself,  some  of 
them  do  injuriously  atfect  the  cane.  Chief  amongst  these  are  the 
species  of  Hahtoncus  (H.  fetragoinis  and  H.  iiiuudus)  and  two 


27 

or  three  species  of  Ccvpophilits  (C.  uiaculafiis  and  C.  diinidialiis) , 
two  or  more  of  these  insects  being  often  present  in  the  same  cane- 
lields.  Breeding-  as  they  do  in  the  parts  attacked  by  the  young 
leaf-hcppers,  they  certainly  add  to  the  injury  bv  increasing  fer- 
mentation and  decay. 

It  may  be  noted  in  passing  that  some  of  the  above  mentioned 
species  are  under  ordinary  circumstances  not  infrequently  a 
source  of  considerable  loss,  owing  to  the  fact  that  where  seed 
cane  is  allowed  to  lie  around  before  planting  they  frequently  lay 
their  eggs  m  the  slightly  fermenting  ends  of  this  seed.  Such 
seed-cane  when  planted  will  in  some  cases  entirely  fail  to  sprout, 
since  the  larvae  of  the  beetle  develop  quite  well  under  ground  and 
cause  its  decay,  and  in  fact  instances  are  known  where  a  very 
large  proportion  of  seed  planted  has  been  ruined  by  these  insects. 
T\Inch  less,  therefore,  under  the  present  circumstances  should  seed 
cane  be  left  exposed  for  these  insects,  now  so  abnormally  numer- 
ous, to  deposit  their  eggs  in,  and  if  not  planted  wdien  cut,  nor  pro- 
tected, it  might  well  be  given  treatment  with  corrosive  sublimate. 
(See  Appendix,  note  I  below). 

With  the  more  sluggish  larvae  of  Carpophilus  and  Haptoncus 
there  are  frequently  found  the  active  larvae  of  one  or  two  spe- 
cies of  Ciuujidac  or  Cryptophagidac,  and  it  is  quite  likely  that 
these  may  prey  on  the  former.  Otherwise,  excepting  that  they 
are  rarely  killed  by  fungus  diseases,  they  appear  to  have  no  ene- 
mies. 

Similarly  breeding  in  the  parts  injured  by  the  leaf-hopper,  and 
adding  to  the  injury,  may  be  mentioned  several  Diptera,  notably 
species  of  Drosophila,  which  are  extremely  abundant  on  some 
plantations,  Euxcsta  annonnc  commonly  and  another  Ortalid  in 
one  or  two  instances. 

Again  with  these  (in  abundance  locally)  were  two  species  of 
Stapliylinidac,  the  common  imported  Hoiiialola  so  frequently  at- 
tracted by  fermenting  vegetable  matter,  and  a  common  Philoii- 
tJius. 

Finally,  there  may  be  casuallv  mentioned  a  host  of  more  or 


2a 

less  conspicuous  insects,  not  ordinarily  seen  in  numbers  in  the 
cane-fields,  the  species  varying  very  much  according  to  locality,  but 
all  attracted  by  the  sweet  excretions  of  the  leaf-hopper. 

Species  of  Sarcophaga,  Eristalis  punctulatus,  Volncella  ohcsa, 
the  little  cockroach,  Phyllodromia  hicroglypJiica,  and  common 
Hciniptcra  being  the  most  conspicuous.  Possil)ly  with  these 
should  be  included  the  three  Elaleri(lai\  Aeolus  cinnamoineus  in 
many  localities,  and  two  native  species,  Eopcnthcs  Kouac  and 
Jtodacnus  sp?  only  in  proximity  to  the  ijative  forests.  Feeding  on 
the  black  fungus  may  be  found  certain  minute  Psocidae,  one  ex- 
tremely small  and  pretty  species  being  in  countless  numbers  on  al- 
niost  all  plantations.  None  of  the  insects  in  this  last  section  can 
be  considered  in  any  way  beneficial  or  injurious,  excepting  that 
they  may,  and  ])robably  do,  carry  and  spread  the  spores  of  nox- 
ious fungi. 

IMPOSSIBILITY   OF   EMPLOYING  ARTIFICIAL    MEANS   TO   DESTROY 
LEAF-IIOPPER. 

13.  When  one  is  acquainted  with  the  habits,  of  the  leaf-hopper, 
its  mode  of  feeding,  the  love  of  concealment  shown  by  the  larger 
number  of  individuals,  the  hidden  eggs,  present  in  numbers  at  all 
reasons ;  and  at  the  same  time  accpiainted  with  the  mode  of  growth 
of  a  thrifty  cane-field,  the  question  of  insecticides  as  a  mode  of 
repression  cannot   for  a  moment  be  entertained. 

As  the  leaf-hopper  is  attracted  with  great  facility  to  strong 
lights,  I  thought  it  possible  that  until  imported  natural  enemies 
were  available  these  nu'ght  be  employed,  as  unquestionably  myr- 
iads might  be  attracted  and  caught  in  receptacles  containing  sticky 
or  oily  fluids,  placed  just  beneath  the  lights,  on  still  dark  nights. 
I  am  told  by  managers  of  plantations,  who  are  naturally  the  best 
judges,  that  on  account  of  the  expense  involved,  such  a  plan  is  im- 
possible. 

POSSIBILITY     OF     NATURAL     ENEMIES     REING     OBTAINED     F130M 
OTHER   COLTNTRIES. 

14.  To  any  one  who  has  paid  attention  to  the  list  of  natural  ene- 


29 

mies  of  the  leaf-hoppar  now  present  in  these  islands,  as  above  enu- 
merated ;  who  considers  that  ah  these  were  available  in  these 
small  islands,  with  their  infinitessimally  small  insect  fauna,  as 
compared  w  ith  that  of  the  rest  of  the  world ;  who  will  take  the 
trouble  to  investig-ate  the  admirable  work  done  by  some  of  these 
natural  enemies,  there  can  be  no  doul)t  whatever  but  that  an  abun- 
dance of  additional  enemies  can  be  introduced  from  other  coun- 
tries. 

r  have  already  in  earlier  reports  stated  that  good  enemies  of 
leaf-hoppers  are  to  be  found  in  certain  Australian  lady-birds.  I 
have  since  learnt  that  Mr.  Koebele  himself  observed  such  enemies 
on  his  former  trip  to  Australia.  That  many  enemies  of  leaf-hop- 
per otlier  than  lady-birds  can  be  found,  there  is  no  doubt  whatever, 
some  are  already  well  known. 

SUMMARY  AND  CONCLUSION. 

15.  In  the  foreg'oing'  pages  I  have  dealt  with  the  history  of  the 
leaf-hopper  since  its  importation  into  the  islands,  its  probable  na- 
tive home,  its  efifect  on  cane  and  different  varieties  of  cane,  its 
haliits,  the  various  other  insects  that  accompany  it,  whether  in- 
jurious or  otherwise  ,  the  impossibility  of  using"  insecticides  against 
it,  and  the  possibility  of  securing  effective  natural  enemies  from 
other  cor.ntries.  More  especially  have  I  considered  the  various 
natural  enemies,  animal  or  vegetable,  alread)^  present  here,  and 
the  parasites  with  which  some  of  these  natural  enemies  are  them- 
selves inrticted. 

The  fine  work  done  by  some  of  the  natural  enemies  now  pres- 
ent, added  to  the  fact  that  as  good  or  better  ones  can  surely 
be  imported  from  other  countries,  can  leave  no  doubt  whatever  in 
the  mind  of  any  entomologist  who  has  investigated  the  matter,  that 
the  leaf-hopper  can  be  so  far  eliminated  by  these  means  as  to  be- 


80 

come  as  innocuous,  as  are  now  a  score  of  what  were  once  some  of 
I  he  worst  pests  here. 

For  some  of  these  latter  one  mav  now  go^  a  long  day's  march 
in  search  without  success.  So  far  as  the  economic  entomologist  is 
concerned  they  are  practically  non-existent,  and  the  ordinary  man 
has  even  forgotten  that  they  ever  existed. 

I  further  helieve  that  even  with  the  aid  of  the  natural  enemies 
availahle  here  on  the  spot,  that  hy  a  constant  watching  for  an  in- 
crease of  the  pest  and  by  transporting  large  numbers  of  the  most 
efficient  of  its  enemies  to  a  spot  threatened  with  a  bad  outbreak, 
the  damage  done  by  leaf  hopper  could  be  reduced  to  small  propor- 
tions. Obviously  in  the  long  run  it  will  prove  much  more  econ- 
omical to  send  away  for  additional  natural  enemies.  A  few,  or  it 
may  be  even  one,  species  of  parasite  or  predaceous  insect  success- 
fully introduced  would  render  it  unnecessary  to  pay  further  at- 
tention to  the  pest. 

It  is  amusing  to  read  the  advice  given  by  the  leading  English- 
speaking  entomologist  of  a  former  day,  the  late  Prof.  Westwood 
of  Oxford,  to  the  Grenadan  planters  on  a  bad  outbreak  of  leaf- 
liopper  occurring  in  their  island. 

"1  can  see,"  he  says,  "but  little  ground  for  coming  to  any  other 
conclusion  than  that  man  will  not  be  permitted  to  frustrate  the  in- 
tention of  Providence,  but  that  we  must  look  alone  with  submission 
to  that  Power  for  the  removal  of  these  pests." 

No  doubt  the  religious  feeling  which  inspired  the  above  re:naiks 
is  very  pleasing  to  contemplate,  but  the  advice  to  do  nothing  is  now 
a  little  out  of  date,  not  to  say  ridiculous,  in  the  light  of  our  pres- 
ent knowledge.  It  must,  however,  be  remembered  that  this  ad- 
vice was  given  three-quarters  of  a  century  ago  (1833)  and  econ- 
omic entomology  has  advanced  somewhat  since  those  days. 


31 


Note  I.  From  the  following  experiments  made  by  Mr.  C.  F. 
Eckart  it  will  be  seen  that  treatment  with  corrosive  sublimate  solu- 
tion is  the  most  effective  cure  for  seed-cane  containing  eggs  of  leaf- 
hopper,  since  it  does  not  injure  this  seed. 

RELATIVE  RESISTANCE  OF  LEAF-HOPPER  EGGS  TO 
HYDROCYANIC  ACID  GAS,  CORROSIVE  SUBLI- 
MATE, AND  CARBOLIC  ACID. 

Sections  of  cane,  eight  inches  long,  were  cut  from  badly  affected 
one-year  old  cane.  The  sections  were  selected  as  a  rule,  from  the 
youngest  parts  of  the  sticks,  and  only  such  portions  were  taken 
as  bore  evidence  of  hopper  eggs  having  been  recentlv  deposited. 
The  pieces  of  cane  so  selected  w^ere  then  well  mixed  and  lots  of  ten 
sections  were  taken  at  random  for  use  in  each  of  several  experi- 
ments. 

The  treatment  to  which  the  several  lots  of  cane  were  subjected 
was  as  follows : 

(i)  Immersion  in  i^  solution  of  corrosive  sublimate  for  3  liours. 
(2}  '*'  "  i^  solution  of  corrosive  sublimate  for  6     " 

(3)  ■'  "  2;/,  solution  of  corrosive  sublimate  for  3     " 

(4)  "  "'   li  solution    of    carbolic    acid    for    3     "' 

(5)  "  ■''   I'/c  solution    of    carbolic    acid    for    6     " 

(6)  "  "  2'/c  solution    of    carbolic    acid    for    3     " 

(7)  Fumigation  for  24  hou  rs  with  Hydrocyanic     Acid 

Gas  (one  ounce  of  Cyanide  of  Potassium  for  27  cu. 
ft  of  space). 

(8)  Untreated  cane  (8  sections). 


32 

After  treatment  the  respective  lots  were  placed  in  boxes  with 
tig-ht  fitting-  glass  tops,  and  at  intervals  of  from  two  to  three  days 
tlie  young  hoppers,  which  had  hatched  out,  were  counted  and 
killed. 

The  various  solutions  of  Carbolic  acid  were  found  inefifective  in 
destroying  the  hopper  eggs,  and  the  counting  in  such  test  was 
discontinued  after  one  week. 

The  tests  were  started  on  Februarv  21st,  1903,  and  the  number 
of  hoppers  counted  on  diiferent  dates  appear  in  the  table  below. 
The  figures  for  carbolic  acid  given  under  date  of  February  28th, 
are  for  the  week  preceding,  only  one  count  having  been  made : 


00000 
o  o  o  o  T 
00000 


K"   o 


to 

to          4 

;^ 

to 

GO 

0           +- 

VI 

0 

0 

0 
-i 

000000 

O     O     O     O     O     I 

000000 


4 

56 

■ 

• 

5 

3 

6 

3 

. 

. 

7 

...  0 

0 

0 

0 

0 

0 

0 

I 

0 

0 

I 

8 

...  0 

2 

21 

25 

24 

3^ 

19 

36 

22> 

19 

200 

Another  series  of  experiments  was  conducted  with  similar  lots 
of  cane,  to  note  the  elTect  of  fumigating  sections  of  stalk  with  Hy- 
drocyanic acid  gas  for  varying  lengths  of  time,  one  ounce  of  Cy- 
anide of  Potassium  being  employed  for  27  cu.  ft.  of  space.  It  was 
also  determined  to  merely  dip  other  sections  in  Corrosive  Subli- 
mate and  compare  the  results  with  those  obtained  where  the  cane 
was  soaked  in  such  solutions. 


33 

The  tests  may  be  designated  by  the  following  numbers : 

(t)  Fumigation  with  Hydrocyanic  Acid  (ias  for  24  hours. 

(2)  "  "  Hydrocyanic  Acid  Clas  for  12     " 

(3)  "  "  Hydrocyanic  Acid  Gas  for     6     " 

(4)  "  "  H}-drocyanic  Acid  Gas  for     3     " 

(5)  Dipping    in     :{:;«;' Corrosive  Sublimate  Solution. 

(6)  "  "      1^'  Corrosive  Sublimate  Solution. 

(7)  "  "      i;^  Corrosive  Sublimate  Solution. 

(8)  ■'  "'      2'/  Corrosive  Sublimate  Solution. 

The  canes  were  put  in  boxes  as  in  the  preceding  experiment  and 
tlie  insects  hatching  out  were  counted  from  time  to  time  and  killed. 
The  numbers  of  hoppers  found  on  different  dates  were  as  follows: 


1    o 

2    o 

3    o 

4    o 

5    o 

6    o 

7   o 

8    o 


0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

4 

0 

I 

0 

0 

0 

0 

2 

0 

0 

0 

I 

6 

0 

0 

0 

0 

0 

1 

0 

0 

I 

0 

0 

I 

0 

0 

0 

0 

The  gas  was  found  to  be  very  effective  in  destroying  the  eggs, 
vvhen  the  cane  sections  were  fumigated  for  periods  of  6  hours  and 
over.  C)f  the  Corrosive  Sublimate  solutions,  2'^.  appeared  the 
most  effective,  only  allowing  one  insect  to  appear. 


84 

After  treatment  as  above  described,  one  hundred  eyes  for  each 
test  were  planted  to  note  the  effect  of  Corrosive  SubHmate  and  Hy- 
drocyanic Gas  on  germination : 

No.  of  Test.  .  Percentage  of  Eyes  Which  Germinated 

1     2 

2    7 

3    36 

4    Not  planted 

5  70 

6  57 

7  73 

8  70 

It  is  seen  that  the  length  of  time  that  the  seed  cane  was  in  con- 
tact with  the  gas  had  a  marked  effect  on  the  vitality  of  the  eye. 
Corrosive  sublimate  apparently  exerted  no  injurious  influence  as 
far  as  germination  was  concerned,  except  in  the  case  of  a  -1^  so- 
lution. It  is  quite  possil^le  that  the  difference  in  the  percentage 
of  germinating  eyes,  between  test  No.  6  and  7  was  quite  acci- 
dental, owing  to  some  slight  difference  in  quality  of  seed  cane 
before  treatment. 

Cane  which  had  been  soaked  for  several  hours  with  ife  and  2^ 
solutions  of  Corrosive  sublimate  was  not  planted,  but  the  eyes  of 
such  cane  showed  remarkable  vitality  in  the  glass  covered  boxes. 
At  the  end  of  a  month's  time,  shoots  six  inches  long  projected  from 
the  canes. 

The  length  of  time  in  which  leaf-hopper  eggs  may  remain  un- 
hatched  in  the  cane  stick  may  be  seen  from  the  following  figures, 
which  embrace  a  continuation  of  the  count  of  insects  hatching  in 
untreated  canes.  (Test  No.  8,  started  Feb.  21)  : 


35 

Date  of  Count.  Insects  Found. 


Feb.     21 


o 


22 

"         24 ^' 

"        26 25 

"        28 24 

^lar.      2.' 3^ 

"           4 ^9 

"           7 36 

lO «J 

12            19 

"         14 ^6 

'•         i8 ^0 

"            20 ^^ 

"         23 -^ 

''         25 3 

•'         28 ■  -+ 

"         3T 3 

April      2 

••  i6 

"         i8 

.  . .  o 


^  ^  ,  261 

Total 

Note  II.     Varieties  of  Cane. 

The  following  list  of  new  varieties-^^  of  cane  at  the  Hawaiian 
Planters'  Experiment  Station  has  been  drawn  up  for  me  by  Mr. 
C.  F.  Fckart.  the  Director.  They  are  arranged  in  order,  accord- 
ing to  the  amount  of  damage  sustained  from  leaf-hopper  attack, 
Queensland  4  suffering  most  and  Yellow  Caledonia  least: 

*  i.  e.  Varieties  other  than  the  old  standard  ones  of  these  islands. 


(0 

Oncensland  4 

(2) 

Queensland  1 

is) 

Queensland  8  A. 

(4) 

Louisiana  Purple 

(5) 

Demerara  95 

(6) 

Gee  Gow 

(7) 

Cavengerie 

{^) 

Demerara  74 

.S(5 

(9)  Yellow  Bani1)oo 

(10)  Tiboo  Merd 

(11)  Louisiana  Striped 
(  12)    Striped  Singapore 

(13)  Big  Ribbon 

(14)  Queensland  7 

(15)  Demerara  ii/' 

(16)  White  Bamboo 
(17)   Yellow  Caledonia. 

NoTic  111.     Description  of  Parasite  of  Canc-Lcaf  ffoppcr. 

I  here  give  the  characters  of  a  highly  interesting  and  import- 
ant Hymenopterous  parasite  of  the  leaf-hopper,  for  which  it  is 
necessary  to  make  a  new  generic  name.  Its  life  history  has  l)e:n 
partiall)-  written  in  the  earlier  part  of  this  report. 

Ecthrodelphax — New  genus : 

Generally  similar  in  structure  to  GoiiatoMis  Pcrkinsi  Ash  in., 
but  winged,  anrl  the  thorax  consequently  much  modified. 

Anttnnae  evidently  thickening  towards  the  apex,  second  joint 
of  the  flagellum  very  elongate  and  slender,  first  much  shorter  and 
thicker,  about  equal  to  third  in  length.  Head  about  twice  as  wide 
as  the  prothorax,  above  distinctly  concave  between  the  eves,  pos- 
teriorly emarginate.  Prothorax  twice  as  long  as  its  width  at 
])ase,  wider  on  its  anterior  than  on  the  posterior  half.  Mes- 
othorax  greatly  narrowed  in  front,  its  sides  being  strong- 
ly convergent,  the  furrows  crenate,  contiguous  at  the  scutellum 
and  thence  divergent  anteriorly,  so  as  to  enclose  a  narrow  tri- 
angular area.  Tegulae  placed  far  back  on  the  mesothorax.  and 
very  remote  from  the  prothorax.  Legs  as  in  the  Goiiafopns  al>ove 
mentioned,  the  front  trochanters  very  long  and  clavate,  the  apical 
part  being  thickened,  all  the  femora  clavate,  the  basal  part  thick- 
ened ;  claws  of  the  front  tarsi  verv  long,  asvmmetrical,  but  of 


37 

equal  length,  llie  one  knobbed  al  the  apex,  the  other  pointed  and 
both    dentieulate. 

EclJirodclpJuix  Fail  rluldii — New  species  : 

r>lack  ;  the  head  (except  the  eyes  and  a  transverse  band  enclos- 
ing the  ocelli)  the  prothorax,  tegulae,  wing  nervures,  the  legs 
entirely  or  almost  so.  a  median  transverse  abdominal  liand 
beginning-  on  the  apical  part  of  the  second  segment,  all  pale  in 
color,  from  yellowish  to  rufo-testaceous.  Head  above,  mesotho- 
rax  and  abdomen  shining;  propodeum  transversely  strigose.  gen- 
erally more  regularly  so  posteriorly.  Antennae  dark,  base  and 
tips.     Length  2.5  mm.   (but  variable.     Female  onlv  known.''' 

n.\r..    If\WAl]AN    ISLANDS. 

(Obs. — This  inseci  would,  under  the  latest  scheme  of  classifi- 
cation of  the  ffyiaciiortcra  proposed  1)\-  Ashmead,  be  placed  with 
the  Sphccoidca,  since  the  wings  are  remote  from  the  prothorax. 
It  has,  however,  no  relationship  witli  that  group.) 

Note  IV.     Dcscrithiou  of  Coiic  Lcaf-Hoppcr. 

The  f(jllowing  is  a  brief  technical  descri])tiou  of  the  cane  leaf- 
liiipper,  Pcrkiiisiclla  saccluvicidd.  Tl  is  condensed  from  Kirk- 
aldy's  original  description  (Entom.  up3.  ]).  179). 

Second  segment  of  the  antennal  peduncle  about  one-half  longer 
than  the  first,  which  is  mucli  wider  at  the  apex  than  basally,  flat- 
tened and  explanate. 

Long-w'inged  form  both  sexes.  Tegmina  elongate,  narrow,  ex- 
tending far  beyond  apex  or  abdomen,  interior  half  of  clavus  and 
cerium  more  or  less  smoky,  a  long  dark  smoky  stripe  on  the  mid- 


*  Since  the  above  description  twas  .icnl  to  ^jrr.s.v  T  Iiurt:  Jind  uiany  inales  of  this  parasite 
These  have  not  the  peculiar  characters  seen  in  thr  th'unx  awl  lajs  of  the  female,  and  seem 
very  similar  to  the  Hawaiian  Labeo,  .so  t-hat  I  have  some  snspicion  that  tite  latter  will  prove 
to  be  the  male  of  Gonatopus. 


38 

die  of  membrane,  three  or  four  nervures  of  the  latter  smoky  at 
apex.     Length  with  wings  6|  mill. 

Short-winged  female.  Tegmina  reaching  onlv  to  base  of  fifth 
segment,  tegmina  without  the  smoky  markings  of  the  long-winged 
form,  the  neuration  similar  but  shortened. 


The  following  table  will  distinguish  the  known  cane  leaf-hop- 
pers, except  DcJphax  saccharivora  of  the  West  Indies,  of  which 
I  have  no  description  to  hand.  Only  tlie  long  winged  forms  are 
considered.  The  characters  are  partly  taken  from  Kruger's  work 
on  sugar-cane: 

A.  Front  wings  twice  as  long  as  the  hind  ones;  hind  tibae  with- 
out long  spur PJicnicc  maculosa.    (Java,   India?) 

A.A..     Front  wings  not  twice  as  long  as  the  hind  ones ;  hind  tibae 
with  long  spur. 

B.  Front  wings  of  a  uniform  brown  color 

Euiuclopina  Kntgcri  (Java.  Borneo) 

BB.     Front  wings  not  uniformly  brown. 

C.  Wings  much  longer  than  the  hind  body 

PcrkinsieUa    Saccharicida.       (Australia,    Hawaii) 

CC.     Wings  not  much  longer  than  the  hind  body 

Dicrav.otropis   vastatrix    (Java) 


